Alley at the NAS Panel

Richard Alley has been a prominent figure in climate change debate. Again we were told to expect a fire-and-brimstone presentation with warnings about tipping canoes. His presentation was lively, but, like Schrag, Alley expressed great caution about what could legitimately be expected from paleoclimate studies and made some very interesting remarks about the disconnect between what policy-makers wanted and what academics could provide.

Here are some striking observations from Alley, which I’ll flesh out below. Alley said that the records mostly stop before the present warming, adding that there is “no coordinated effort to update paleoclimate data, to obtain a clear picture of the last decades in the context of the millennium”. Alley said that paleoclimatologists usually collect records for other reasons and “policy-makers are trying to squeeze the process”. He said that the “community could do better if that was a high priority”, later saying that “we have a tremendous ability to do better”. He said that we “had not really integrated them [polar cores] in a coherent way”, because “this was “not the highest priority of the scientific community”. He thought that updating records was merely “operational” and not something that you could ask a Ph.D. to do.

Alley’s at Penn State; he noted that he had been a coauthor and supervisor for panellist Cuffey (but did not mention that co-presenter Mann was also at Penn State.) Alley led off by saying that the paleoclimate network was not designed to answer questions about climate change. He said that he liked glaciers, especially when they “behaved badly”, that glacier increase(decrease) mostly reflected summer temperature. An increase of 1 deg C was roughly correlated with 25% mass loss; while it also led to increased precipitation of about 7%. The order of magnitures were close enough that some anomalous individual results existed. Later he qualified these percentages by saying that they applied to glaciers with land termini, while glaciers with ocean termini were less sensitive.

He presented the Oerlemanns graphic (now being commonly used in spaghetti graphs) going up to 1990, together with updates after 1990 from Dyurgerov and Meier [2005], a “wonderful” report in the “grey literature”, “grey literature” here apparently being Occasional Paper 58 of the Institute for Alpine and Arctic Research. (SM: In passing, it is remarkable that a detailed and systematic presentation should be regarded as “grey” literature while articles that are, at best, extended abstracts in Nature and Science are not. Dyurgerov and Meier is online — see link below.)

Alley said that glaciers were not starving and glacier recession was not due to lack of precipitation. He showed a temperature reconstruction for Greenland from Cuffey et al. 1995, in which Alley said that high-frequency isotope data was combined with borehole data to yield composite. (SM: An editorial note: the graphic posted up by Alley did not show that 20th century temperatures had passed above MWP levels, although Alley did not mention this and none of the panellists asked him about it.) Alley also showed a melt layer stack, but I did not pick up the provenance.

A further editorial aside: data is archived at WDCP for Alley [2000] here , which provides as an additional reference Cuffey and Clow [1997]. (I’ve consulted Cuffey and Clow [1997] but haven’t consulted Cuffey et al 1995 yet). Here’s the latter portion of Cuffey’s reconstruction as archived, which at least also shows the same feature of medieval-modern levels as the graphic presented by Alley. (Dates in BP converted to 1950. GISP results come much later than shown in the data archived at this file, perhaps due to the smoothing by Alley [2000]. The data in Alley [2000] goes back to 43000BP, the main purpose of the reconstruction being to illustrate the difference between LGM and Holocene results and the MWP illustration here is incidental to the original article.) Obviously it shows a pronounced MWP peaking at the exact point of Viking exploration. Cuffey’s reconstruction is not used in any Hockey Team reconstructions. I’m going to post up some remarkably different temperature histories from Greenland, showing the curious spaghetti that may exist in even one locale.

Alley said that the records mostly stop before the present warming, adding that there is “no coordinated effort to update paleoclimate data, to obtain a clear picture of the last decades in the context of the millennium”. He said that the “community could do better if that was a high priority”.

Alley then showed 6 àÅ½àⳏ18 isotope series from Thompson’s tropical glaciers: Dasuopu, Dunde and Guliya in the Himalayas; Huascaran, Sajama and Quelccaya in South America). He acknowledged that the isotopic picture is “complicated” and then showed a composite “interpreting” the àÅ½àⳏ18 as temperature.

The àÅ½àⳏ18 values in tropical glaciers are seasonally reversed from polar glaciers, adding a huge and arguably insuperable problem to the extraction of temperature data from tropical àÅ½àⳏ18 ice cores. In polar glaciers, summer àÅ½àⳏ18 values are high and winter àÅ½àⳏ18 values are low; thus, while changing sources are an important issue in the interpretation of polar isotopes, one is beginning with a plausible temperature interpretation of the isotopes. In tropical glaciers, the situation is reversed. Summer àÅ½àⳏ18 values are low (coming from monsoon rainout both in the Himalayas and Andes) and winter àÅ½àⳏ18 values are high. In looking at the past, high àÅ½àⳏ18 spikes at (say) Dasuopu are interpreted even by Lonnie Thompson as associated with monsoon failures (thus reduced summer precipitation). The association of tropical ice core àÅ½àⳏ18 with precipitation is called the “amount effect”. Despite this, Lonnie Thompson argues that increases of annual àÅ½àⳏ18 values in the 20th century should this be interpreted as evidence of increased temperature; however, other specialists have, in my opinion, convincingly argued that it is due to changes in precipitation. Alley did not disclose this problem to the panel when he presented the àÅ½àⳏ18 information and no one on the panel asked Alley about the “amount effect” in tropical precipitation. (BTW the ice core information used by Alley had not been archived in 2004 and was archived by Thompson at the direction of Climatic Change only after a great deal of correspondence and formal complaints from me.)

Alley proceeded to discuss meltwater penetration at the top of Quelccaya (Coriocalis). He mentioned that there was plant material dated 5000 years old. Thus “some indication that we had moved out of the range of natural variability”. Again I’d like to pin down the information on these organics; Thompson’s use of radiocarbon dates of organics in glacier dating at Kilimanjaro seems highly questionable to me.

Alley then discussed some of the practical issues related to collection of proxies in a policy context, saying that “we have a tremendous ability to do better”. He said that we “had not really integrated them [polar cores] in a coherent way”, because “this was “not the highest priority of the scientific community”. Alley said that paleoclimatologists usually collect records for other reasons and “policy-makers are trying to squeeze the process”, throwing in a complaint about funding. He asked: “What science department would hire someone to update an ice core record? You couldn’t tell a Ph.D to do this. It was more akin to operations.” He said that “the proxies are not designed to answer the questions…We know we can do better… If you want to do it right, it has to be operational”.

Cuffey: Can you tell the average temperature 1000 years ago to within 0.5 degree C? Alley: No.

Alley’s coments about updating raise lots of questions and issues, which I’ll come back to. If I were a policy-maker funding paleoclimatologists, I’d sure be surprised by some of Alley’s answers.

6 Comments

In passing, it is remarkable that a detailed and systematic presentation should be regarded as “grey” literature while articles that are, at best, extended abstracts in Nature and Science are not.

I would assume "grey" is a reference to the fact that INSTAAR Occasional Papers are not peer-reviewed in the traditional sense since it is a mechanism by which The Institute of Arctic and Alpine Research publishes the work of its own scientists. I would agree though that some technical reports like this are worth a great deal more than some of the formally peer review literature.

Steve: Thanks. I’ll fix this and edit my post. Alley’s data seems to be heavily rounded. I wonder what a less smoothed version looks like. I wonder if Alley will provide it.

very interesting remarks about the disconnect between what policy-makers wanted and what academics could provide.

It looks to me that they went with what some “policymakers” wanted, which seems to be common in climate change reporting.

I am not sure I understand your comment. Are you suggesting the policymakers threatened the scientists with higher taxes if they didn’t “improve” the reported uncertainty in the paleoclimate reconstructions or rewrite the summary for policymakers?

Traditional problems with ice core temperature reconstructions are well known. You measure the isotopes of the precipitation, containing more variables than temperature alone. But you only measure those “temperatures” when it snows. Obviously, summer and winter snow has a totally different signature. Which also means that a climate shift (which happens all the time) that changes the summer winter precipitation ratios also changes the accumulated isotope ratios in the ice cores.

with one main conclusion: when it snows the temperatures are above average. Now, the annual snow accumulation on the Greenland summit ice core, the source of the Alley2000 temperature, rides the same thrilling rollercoaster as the isotope ratios but this type of behavior was not reckoned with in that time of Alley2000. So, a fundamental revision of ice core temperature reconstructions should be expected.

I realize this comment string is probably too old post to with any relevancy, but here is a new development from Dr. Richard Alley of Penn State that I have read in EOS Transactions (27 Sept. 2011, Volume 92 no. 39). He has chaired a committee which developed the contents for a new exhibit at the Washington, DC – based Marian Koshland Science Museum of the National Academy of Sciences. This exhibit is titled “Earth Lab; Degrees of Change”. It includes an interactive carbon-management simulator. The EOS article claims that the exhibit is based on authority from an National Academy of Sciences (NAS) affiliated publication “America’s Climate Choices Reports”, which concludes that “climate change is occurring, is very likely caused by human activities, and poses significant risks for a broad range of human and natural systems”.